Brake device for vehicle and method for controlling the same

ABSTRACT

The present disclosure relates to a brake device for a vehicle, and a main object of the present disclosure is to provide a brake device for a vehicle which can stably perform an electric parking braking cooperative control process for dynamic parking braking in a state in which the brake device enters a backup mode due to an abnormality or a malfunction generated in a device related to an electric booster in a vehicle equipped the electric booster. In order to achieve the above object, a brake device including a fallback valve which is provided on a hydraulic pressure supply line connected to a wheel brake of a wheel on which an electronic parking brake is installed, and which is configured to selectively shut off brake liquid pressure supplied to the wheel brake, and a method for controlling the same are disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.16/199,771, filed on Nov. 26, 2018, which claims the benefit of priorityto Korean Patent Application No. 10-2018-0122246 filed on Oct. 15, 2018with the Korean Intellectual Property Office, the entire contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a brake device for a vehicle and amethod for controlling the same, and more particularly, to a brakedevice for a vehicle which can stably perform an electric parkingbraking cooperative control process for dynamic parking braking in astate in which the brake device enters a backup mode due to anabnormality or a malfunction generated in a device related to anelectric booster in a vehicle equipped the electric booster, and amethod for controlling the same.

BACKGROUND

Generally, a brake device for a vehicle includes a boosting device, thatis, a brake booster installed between a brake pedal and a mastercylinder, and the brake booster increases pedal operational force (i.e.,pedaling force) which is a force applied to a brake pedal by a driver,and transmits it to the master cylinder.

Commonly, the brake booster is configured to increase the brake pedaloperational force by using difference in air pressure between vacuumpressure (negative pressure) and atmospheric pressure provided on anintake side of an engine, and the master cylinder is coupled to aforward cell forming a constant pressure chamber to enable hydraulicpressure to be generated by using increased force.

The above brake booster includes an input rod that receives force fromthe brake pedal and an output rod that outputs increased force, and thebrake booster transmits output greater than the input, that is, forceapplied to the brake pedal, to the master cylinder through the outputrod when the driver presses the brake pedal to allow the hydraulicpressure to be smoothly generated in the master cylinder.

Therefore, the brake booster reduces force required when the driveroperates the brake pedal.

Meanwhile, an integrated electric booster (IEB) that uses an electricmotor as a boosting force source has been known in the break booster forreducing force required when the brake pedal is operated.

Such the integrated electric booster is an electric device that utilizesforce of an electric motor other than mechanical engine negativepressure to increase the force, when a controller controls operation ofthe electric motor based on an operational amount of the brake pedaldetected by a sensor, a piston is moved forward by a rotational motionof the electric motor to enable necessary hydraulic pressure to begenerated in the master cylinder.

Since the electric booster does not need to utilize the negativepressure of the engine as described above, there is an advantage thatthe integrated electric booster can be applied to an environmentallyfriendly vehicle such as an electric vehicle which is not equipped withan engine. However, since the electric booster is an electric systemother than a mechanical type device, there is a high possibility thatthe electric booster is switched to a backup mode due to electricinfluences such as a low voltage or a circuit burnout.

However, when the actual backup mode occurs, braking assist force isrequired due to a sudden drop in the braking deceleration.

In the backup mode, a collision accident may occur due to lack ofbraking force. In addition, even when the brake device enters the backupmode after a malfunction is detected, since it is only necessary tosatisfy a certain level of regulatory specifications, it is possible tosatisfy the actual regulations under the malfunction condition. However,when operating the brake pedal, the driver may actually feel that pedaloperation is stiff at the beginning and simultaneously feel as ifbraking deceleration of the vehicle is hardly formed.

Accordingly, as a solution to the above problem, a method of assistingbraking deceleration by using an electronic parking brake (hereinafter,referred to as “EPB”) of a rear wheel when the electric booster isswitched into the backup mode in a vehicle equipped with the integratedelectric booster may be considered.

That is, this method assists the braking deceleration of the vehicle inthe backup mode when a vehicle is in running state, not in parking byutilizing dynamic parking brake technology, which is an additionalfunction of an EPB caliper of the rear wheel.

In a vehicle equipped with the conventional integrated electric booster,however, it is extremely difficult to perform cooperative controlassisting the braking deceleration by using the dynamic parking brakingof the actual EPB in the backup mode.

Since a cut valve, which is a normal open (NO) type valve, is in an openstate in the backup mode, when the driver presses the brake pedal inthis state, liquid pressure caused by a pedaling force is alsotransmitted to the caliper of the rear wheel. Accordingly, in aninternal state of the caliper of the rear wheel in which the liquidpressure is already formed as described above, it is difficult toperform EPB cooperative control, that is, the dynamic parking brakingcontrol.

In a state in which the liquid pressure of the master cylinder caused bythe driver's pedaling force is being transmitted to the caliper of therear wheel, when the EPB cooperative control for generating the brakingforce in the EPB, that is, the cooperative control allowing an EPBactuator to exert separate force on the caliper of the rear wheelcaliper is performed, a rear wheel lock phenomenon may occur, and due tothis phenomenon, the vehicle may lose stability and turn around.

For this reason, it is practically extremely difficult to perform theEPB cooperative control for the dynamic parking braking in the backupmode in the conventional brake device to which the integrated electricbooster is applied.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the disclosure andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY

The present disclosure has been made in an effort to solve theabove-described problems associated with prior art.

Accordingly, the present disclosure is devised to solve the abovedescribe problems, and an object of the present disclosure is to providea brake device which can stably perform an electric parking brakingcooperative control process for dynamic parking braking in a state inwhich the brake device enters a backup mode due to an abnormality or amalfunction, such as low voltage or circuit burnout or the like,generated in a device related to an electric booster, and a method forcontrolling the same.

In order to achieve the above object, according to one aspect of thepresent disclosure, the brake device for a vehicle provided with anelectric booster and an electronic parking brake, may include a mastercylinder configured to receive pedaling force outputted from theelectric booster and generate brake liquid pressure; a liquid pressuresupply device configured to generate the brake liquid pressure accordingto a driver's pedal-operational value detected by a brake pedal sensorand supply the brake liquid pressure to a wheel brake of each wheel; ahydraulic pressure supply line connected from the liquid pressure supplydevice to the wheel brake of each wheel to enable the brake liquidpressure to be supplied from the liquid pressure supply device to thewheel brake; a backup line connected from the master cylinder to thehydraulic pressure supply line to enable the brake liquid pressure to besupplied from the master cylinder to the hydraulic pressure supply line;a cut valve disposed on the backup line and configured to selectivelyshut off the brake liquid pressure; and a fallback valve disposed on thehydraulic pressure supply line connected to the wheel brake of the wheelon which the electronic parking brake is installed, the fallback valvebeing configured to selectively shut off the brake liquid pressuresupplied to the wheel brake.

In addition, according to another aspect of the present disclosure, themethod for controlling the brake device for a vehicle provided with anelectric booster and an electronic parking brake and including a mastercylinder configured to receive pedaling force outputted from theelectric booster and generate brake liquid pressure; a liquid pressuresupply device configured to generate the brake liquid pressure accordingto a driver's pedal-operational value detected by a brake pedal sensorand supply the brake liquid pressure to a wheel brake of each wheel; ahydraulic pressure supply line connected from the liquid pressure supplydevice to the wheel brake of each wheel to enable the brake liquidpressure to be supplied from the liquid pressure supply device to thewheel brake; a backup line connected from the master cylinder to thehydraulic pressure supply line to enable the brake liquid pressure to besupplied from the master cylinder to the hydraulic pressure supply line;a cut valve disposed on the backup line and configured to selectivelyshut off the brake liquid pressure; and a fallback valve disposed on thehydraulic pressure supply line connected to the wheel brake of the wheelon which the electronic parking brake is installed, the fallback valvebeing configured to selectively shut off the brake liquid pressuresupplied to the wheel brake, may include the steps of diagnosing a stateof the brake device including the electric booster by a controller, andallowing the brake device to enter a backup mode by the controller in acase where the brake device is in a malfunction state when a driveroperates a brake pedal; generating the brake liquid pressure in themaster cylinder according to the pedaling force as a driver operates abrake pedal; controlling, by the controller, the fallback valve in thebackup mode to become in a closed state; and performing, by thecontroller, dynamic parking brake control in which braking force forvehicle deceleration is generated by using the electronic parking brake.

Furthermore, according to further another aspect of the presentdisclosure, the method for controlling the brake device for a vehicleprovided with an electric booster, an electronic parking brake installedon a rear wheel, a fallback installed on a hydraulic line between amaster cylinder and a wheel brake of the rear wheel in addition to a cutvalve, may include the steps of diagnosing a state of the brake deviceincluding the electric booster by a controller, and allowing the brakedevice to enter a backup mode by the controller in a case where thebrake device is in a malfunction state when a driver operates a brakepedal; generating the brake liquid pressure in the master cylinderaccording to the pedaling force as a driver operates a brake pedal;controlling, by the controller, the fall back valve in the backup modeto become in a closed state; and performing, by the controller, dynamicparking brake control in which braking force for vehicle deceleration isgenerated by using the electronic parking brake.

Other aspects and preferred embodiments of the disclosure are discussedinfra.

It is understood that the term “vehicle” or “vehicular” or other similarterm as used herein is inclusive of motor vehicles in general such aspassenger automobiles including sports utility vehicles (SUV), buses,trucks, various commercial vehicles, watercraft including a variety ofboats and ships, aircraft, and the like, and includes hybrid vehicles,electric vehicles, plug-in hybrid electric vehicles, hydrogen-poweredvehicles and other alternative fuel vehicles (e.g. fuels derived fromresources other than petroleum). As referred to herein, a hybrid vehicleis a vehicle that has two or more sources of power, for example bothgasoline-powered and electric-powered vehicles.

The above and other features of the disclosure are discussed infra.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present disclosure will now bedescribed in detail with reference to certain exemplary embodimentsthereof illustrated the accompanying drawings which are givenhereinbelow by way of illustration only, and thus are not limitative ofthe present disclosure, and wherein:

FIG. 1 is a structural view illustrating a brake device for a vehicleaccording to the prior art;

FIG. 2 is a configuration view illustrating a brake device for a vehicleaccording to an embodiment of the present disclosure;

FIG. 3 is a block diagram illustrating primary components in the brakedevice for a vehicle according to an embodiment of the presentdisclosure; and

FIG. 4 is a flow chart showing a process for controlling the brakedevice for a vehicle according to an embodiment of the presentdisclosure.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variouspreferred features illustrative of the basic principles of thedisclosure. The specific design features of the present disclosure asdisclosed herein, including, for example, specific dimensions,orientations, locations, and shapes will be determined in part by theparticular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present disclosure throughout the several figures of the drawing.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings so that those skilledin the art to which the present disclosure pertains can easily carry outthe present disclosure. However, the present disclosure is not limitedto the embodiments described herein, but may be embodied in other forms.

In the whole description, when a component is referred to as being“comprising” any component, it does not exclude other components, butmeans that this component further comprises the other components unlessotherwise specified.

In order to aid to understand the present disclosure, the constructionand the problems of the conventional brake device are described firstwith reference to the drawings.

FIG. 1 is a structural view illustrating a brake device for a vehicleaccording to the prior art, and illustrates a hydraulic circuit in whicha brake liquid pressure is generated as a driver operates a brake pedal2. In the hydraulic circuit, hydraulic lines 6 and 8 to which hydraulicpressure is supplied are indicated by thick lines.

FIG. 1 illustrates a state in which the brake liquid pressure caused bypedaling force of the brake pedal 2 is transmitted to all of wheelbrakes 28 of front wheels FL and FR and wheel brakes 28 of rear wheelsRL and RR in a backup mode. In this state, dynamic parking brakingcontrol becomes substantially unavailable.

As illustrated, the brake device includes a reservoir 1 in which brakeliquid is stored, a master cylinder 4 generating the liquid pressurewhen the driver operates the brake pedal 2, a pedal simulator 12configured to provide the pedal feel according to the driver's pedalingforce by the liquid pressure generated in the master cylinder 4, thewheel brakes 28 provided on the wheels FL, FR and RL, RR, respectively,a liquid pressure supply device 20 configured to generate the brakeliquid pressure (braking hydraulic pressure), hydraulic lines 6, 8, 8 a,23, 24 connecting the components including the reservoir 1, the mastercylinder 4, the pedal simulator 12, the liquid pressure supply device20, the wheel brakes 28 and the like, and valves 7, 9, 25, 26 and 27provided on the hydraulic lines.

In FIG. 1, reference numeral 3 denotes a pedal travel sensor (PTS),reference numerals 5 a and 5 b denote hydraulic ports through which thehydraulic pressure is discharged from the master cylinder 4, referencenumeral 21 denotes a hydraulic cylinder of the hydraulic pressure supplydevice 20, and reference numeral 22 denotes a piston of the hydraulicpressure supply device 20.

In addition, in FIG. 1, reference symbol M denotes a motor of thehydraulic pressure supply device 20, and reference symbol T denotes apower conversion part of the hydraulic pressure supply device 20.

Referring to FIG. 1, in the conventional brake device, since the cutvalves 7 and 9 are in opened state when the brake device enters thebackup mode, the brake liquid pressure (hydraulic pressure of the mastercylinder) caused by the pedaling force may be applied to all of calipers(wheel cylinders) of the wheel brakes 28, which are provided on thefront wheels FL and FR and the rear wheels RL and RR, through thehydraulic lines 6 and 8.

In a vehicle equipped with an electric booster (not shown), for examplea known integrated electric booster (IEB), when it is not possible toutilize the electric booster due to an abnormality or malfunction, suchas low voltage or circuit burnout or the like, generated in the device,once the brake device enters the backup mode, no power is applied to allthe valves in the conventional brake device as illustrated.

Therefore, the normal open (NO) type cut valves 7 and 9 are opened, andat this time, when the driver presses the brake pedal 2, the brakeliquid pressure (hydraulic pressure) generated in the master cylinder 4by the driver's pedaling force is directly transmitted to the caliper ofthe wheel brake 28 provided on each of the wheels FL, FR and RL, RR.

At this time, since the brake liquid pressure (hydraulic pressure)generated in the master cylinder 4 by the driver's pedaling force istransmitted to the wheel brakes 28 of the rear wheels RL and RR, morespecifically, to the calipers of the rear wheel brakes, it is impossibleto accurately and precisely control operation of an electronic parkingbrake (not shown) (hereinafter, referred to as “EPB”) of the rearwheels.

More specifically, in the backup mode, when the driver operates thebrake pedal 2 to generate braking force in the rear wheel as well as thefront wheel, performing EPB cooperative control (dynamic parking brakecontrol), which precisely controls operation of the EPB of the rearwheels to generate braking force in the rear wheels at a level at whichrear wheel lock is not generated, may be considered for stable vehiclebraking. However, since the cut valves 7 and 9 are opened in the backupmode, the brake liquid pressure of the master cylinder 4 is directlytransmitted to the calipers of the rear wheels RL and RR.

When the brake liquid pressure (i.e., hydraulic pressure in the mastercylinder) generated by the driver's pedaling force is created in andapplied to the calipers of both the rear wheels RL and RR, since thehydraulic pressure has already been applied to the piston in thecylinder each of the calipers of both the rear wheels, forward andbackward control of the piston performed by an EPB actuator cannot beperformed properly in this state.

That is, since the brake liquid pressure and force generated by the EPBactuator (usually, an electric motor) (force of the EPB actuatortransmitted through a gear device) simultaneously exert on the piston inthe cylinder of the caliper, it is difficult to control forward andbackward movement of the piston, and in particular, it is difficult toperform EPB cooperative control for controlling operation of the EPB togenerate the braking force at a level at which a lock of the rear wheelsdoes not occurs.

In the backup mode, if the hydraulic pressure caused by the driver'spedaling force has been already created in the calipers of both the rearwheels, when the EPB cooperative control for dynamic parking braking isperformed, the forward and backward movement of the piston performed bythe EPB actuator cannot be precisely controlled to a required level.

Finally, in the worst case, the brake liquid pressure (hydraulicpressure of the master cylinder) caused by the pedaling force of thebrake pedal 2 and a braking torque generated by force of the actuator(force of the motor) can instantly reach the level of rear wheel lock,and a vehicle may be turned around due to such the rear wheel lock.

Accordingly, the present disclosure is devised to solve the aboveproblem, and provides a brake device which can stably perform electronicparking brake (hereinafter referred to as “EPB”) cooperative control fordynamic parking braking after entering the backup mode in a vehicleequipped with an integrated electric booster (hereinafter referred to as“IEB”), and a hydraulic circuit therefor.

The present disclosure may be applied to a vehicle equipped with theelectric booster and the electronic parking brake, and a main technicalfeature of the present disclosure is that, when the driver presses thebrake pedal 2 while the vehicle is running after entering the backupmode, the brake liquid pressure (hydraulic pressure of the mastercylinder) to the rear wheels can be shut off by using separate valves toallow EPB cooperative control for dynamic parking braking to be stablyperformed even in the backup mode.

Generally, when the vehicle equipped with the EPB is running in a normalmode, rather than in the backup mode, the EPB cooperative control(dynamic parking brake control) which precisely controls the EPB may beperformed so that, when the driver depresses the brake pedal 2, thebraking force, which is required when the vehicle is decelerated, isgenerated at a level at which the rear wheel lock does not occur.

As described above, a braking for generating the braking force fordecelerating the vehicle by using the EPB when the vehicle is in adriving state, rather than in a parking state may be called dynamicparking braking. On the other hand, a braking for the original purposeof fixing the wheels not to allow the vehicle to be moved using the EPBwhen the vehicle is parked may be referred to as static parking braking.

In the conventional brake device, in the normal mode, the cut valves 7and 9 may be maintained in closed state by applying a current, and thusit is possible to allow the hydraulic pressure of the master cylinder 4not to be transmitted to the wheel brakes 28 (calipers) of the rearwheels RL and RR. In addition, in this state, it is possible to performthe EPB cooperative control for the dynamic parking braking.

On the other hand, since, in the backup mode, a current is shut off andthe normal open type cut valves 7 and 9 become in open state, thehydraulic pressure of the master cylinder 4 can also be transmitted tothe wheel brakes 28 of the rear wheels RL and RR. In a state in whichthe liquid pressure is already formed in the rear wheel as above, it isdifficult to perform the EPB cooperative control for the dynamic parkingbraking.

In the present disclosure, therefore, in the backup mode, by shuttingoff the hydraulic pressure to the wheel brakes of the rear wheels usingthe valve that is an additional component, it is possible to allow theEPB cooperative control for the dynamic parking braking to be stablyperformed, and it is possible to avoid the risk of collision caused byinsufficient braking deceleration in the backup mode through the stableEPB cooperative control.

Hereinafter, a brake device for a vehicle and a method for controllingthe same according to an embodiment of the present disclosure will bedescribed in detail with reference to the drawings, and the presentdisclosure will be described with reference to an embodiment in which anelectronic parking brake is mounted on the rear wheels of the vehicle.

FIG. 2 is a configuration view illustrating a brake device for a vehicleaccording to an embodiment of the present disclosure, and shows a statein which the brake liquid pressure caused by the pedaling force of thebrake pedal 2 is not transmitted to the wheel brakes 28 of both the rearwheels RL and RR by the fallback valve 29.

FIG. 3 is a block diagram illustrating primary components in the brakedevice for a vehicle according to an embodiment of the presentdisclosure, and FIG. 4 is a flow chart showing a process for controllingthe brake device for a vehicle according to an embodiment of the presentdisclosure.

Although not shown in FIG. 2, the brake device according to anembodiment of the present disclosure may include an integrated electricbooster (“IEB”) 11 and an electronic parking brake 30 (hereinafter,referred to as “EPB”) as shown in FIG. 3.

In addition, the brake device according to an embodiment of the presentdisclosure further includes an additional valve, that is, the fallbackvalve 29 which can selectively shut off the liquid pressure for thewheel brakes 28 of the rear wheels RL and RR, and remaining componentsexcept for the fallback valve 29 are not different from thecorresponding components of the conventional brake device described withreference to FIG. 1.

In other words, the brake device according to an embodiment of thepresent disclosure may include the reservoir 1 in which the brake liquid(brake oil) is stored, the master cylinder 4 configured to receive thedriver's pedaling force which is increased in and outputted from theelectric booster 11 and generate the liquid pressure when the driveroperates the brake pedal 2, and the pedal simulator 12 configured toprovide the pedal feel according to the driver's pedaling force by theliquid pressure generated in the master cylinder 4.

In addition, the brake device according to an embodiment of the presentdisclosure may further include the wheel brakes 28 provided on thewheels FL, FR and RL, RR, respectively, the liquid pressure supplydevice 20 configured to generate the brake liquid pressure (brakinghydraulic pressure), the hydraulic lines 6, 8, 8 a, 23, 24 connectingthe components including the reservoir 1, the master cylinder 4, thepedal simulator 12, the liquid pressure supply device 20, the wheelbrakes 28 and the like, and the valves 7, 9, 25, 26 and 27 provided onthe hydraulic lines.

The pedal simulator 12 is connected to the master cylinder 4 through abackup line 8 a to receive the liquid pressure generated in the mastercylinder 4.

Further, the brake device according to an embodiment of the presentdisclosure may have a configuration for forming and controlling thehydraulic pressure using an electronic actuator, and such the brakedevice is usually called an electro-hydraulic brake system (EHB), thatis, an electronic hydraulic brake device.

FIG. 2 shows the configuration of the electronic hydraulic brake device,this electronic hydraulic brake device is merely exemplary, and thepresent disclosure is not limited thereto. The present disclosure is notlimited to the electronic actuator. In addition, the present disclosuremay have a configuration of a general hydraulic brake device in whichthe brake liquid pressure is generated and supplied by a conventionalpump, instead of the electronic actuator.

As illustrated, the electronic hydraulic brake device employs anelectronic hydraulic actuator as the liquid pressure supply device 20generating and supplying the brake liquid pressure (braking hydraulicpressure).

The electronic hydraulic brake device which is the liquid pressuresupply device 20 may have a configuration in which rotational forcegenerated in and supplied by the motor M is converted into linear forcethrough the power conversion part T to move the piston 22 forward andbackward and, at this time, the piston 22 which is controlled to bemoved forward and backward pressurizes brake liquid in a chamber of thecylinder 21 to generate and control the hydraulic pressure.

That is, when the driver operates the brake pedal 2, a pedal-operationalvalue is sensed by the brake pedal sensor (PTS) 3, and when a controller(the reference numeral 10 in FIG. 3) controls the motor M of theactuator (the liquid pressure supply device) 20 according to the sensedpedal-operational value, the rotational force of the motor M isconverted into the linear force by the power conversion part T to movethe piston 22 forward and backward, whereby a regulated hydraulicpressure is generated in the cylinder 21. The controller 10 may be anelectric circuitry that executes instructions of software which therebyperforms various functions described hereinafter.

The above-described electronic actuator is a known structure which hasbeen already used in the electronic hydraulic brake device, and thus anadditional description thereof is omitted.

In the brake device according to an embodiment of the presentdisclosure, the wheel brake 28 is a component configured to generate abraking force for restricting rotation of the relevant wheel using thebrake liquid pressure (braking hydraulic pressure) which is generated inthe liquid pressure supply device 20 and transmitted thereto, and theliquid pressure supply device 20 is connected to the wheel brake via thehydraulic lines 23 and 24.

In the brake device according to an embodiment of the presentdisclosure, the hydraulic lines include hydraulic pressure supply lines23 and 24 connecting the wheel brake 28 of each wheel and the liquidpressure supply device 20 and to supply the brake liquid pressure(braking hydraulic pressure), which is generated by the liquid pressuresupply device 20, to each wheel brake 28 and backup lines 6 and 8connected from the master cylinder 4 to the hydraulic pressure supplylines 23 and 24.

The hydraulic pressure supply lines include a first hydraulic pressuresupply line 23 connected from the liquid pressure supply device 20(electronic hydraulic actuator) to the two wheel brakes 28 of the frontwheels FL and FR and a second hydraulic pressure supply line 24connected from the liquid pressure supply device 20 to the two wheelbrakes 28 of the rear wheels RL and

RR.

The valves 25 configured to control a flow of brake liquid are providedon the hydraulic pressure supply lines 23 and 24 between the liquidpressure supply device 20 and the wheel brake 28.

In addition, each of the hydraulic pressure supply lines 23 and 24 isconnected to the wheel brake 28 of each of the wheels FL, FR and RL, RRvia an inlet valve 26, and an outlet valve 27 is provided on a returnline branched from the hydraulic pressure supply lines 23 and 24connected to the wheel brake of each wheel.

Furthermore, the backup lines include a first backup line 6 connectedfrom a first hydraulic port 5 a of the master cylinder 4 to the firsthydraulic pressure supply line 23 and a second backup line 8 connectedfrom a second hydraulic port 5 b of the master cylinder 4 to the secondthe hydraulic pressure supply line 24.

Also, a first cut valve 7 is provided on the first backup line 6, asecond cut valve 9 is provided on the second backup line 8, and all thefirst cut valve 7 and the second cut valve 9 are provided as normal opentype valves.

In the above described configuration, the first backup line 6 and thesecond backup line 8 become a portion of the hydraulic line between themaster cylinder 4 and the wheel brake 28. In the know brake device, whenthe brake device enters the backup mode due to its malfunction, thefirst cut valve 7 and the second cut valve 9 become in closed state (astate in which a current is shut off), so that the first backup line 6and the second backup line 8 function to transmit the liquid pressuregenerated in the master cylinder 4 to the wheel brake 28 of each of thewheels FL, FR and RL, RR.

On the contrary, in a normal mode, the first cut valve 7 and the secondcut valve 9 become in closed state (a state in which a current isapplied) and, at this time, the liquid pressure generated in the mastercylinder 4 is not transmitted to the wheel brake 28 of each of thewheels FL, FR and RL, RR.

The first cut valve 7 and the second cut valve 9 serve to hydraulicallydisconnect the master cylinder 4, the pedal simulator 12 and the brakepedal 2 from the liquid pressure supply device 20, the hydraulicpressure supply lines 23 and 24 and the wheel brake 28, and in a statein which the first cut valve 7 and the second cut valve 9 are closed,the liquid pressure formed and controlled by the liquid pressure supplydevice 20 is transmitted to the wheel brake 28 of each of the wheels FL,FR and RL, RR to generate the braking force.

The pedal simulator 12 is provided to provide a reaction force inresponse to the pedaling force of the brake pedal 2, and may beconnected to the second backup valve 9 between the master cylinder 4 andthe second cut valve 9 via the separate hydraulic line 8 a.

The above-described pedal simulator has a structure known in the brakedevice, and thus an additional description thereof is omitted.

Meanwhile, the brake device according to an embodiment of the presentdisclosure includes a fallback valve 29 which can selectively shut offthe liquid pressure to the rear wheel.

The fallback valve 29 is a component newly added to the presentdisclosure, and is the electronic valve that is installed on the secondhydraulic pressure supply line 24 connected to the wheel brakes 28(calipers) of both the rear wheels RL and RR and is controlled by acontroller 10 to be opened and closed.

More specifically, the fallback valve 29 is installed one the secondhydraulic pressure supply line 24 connected from the liquid pressuresupply device 20 to the two wheel brakes 28 on both the rear wheels RLand RR, and is installed downstream of a point of the second hydraulicpressure supply line 24, where the first backup line 8 is connected.

In addition, unlike the first cut valve 7 and the second cut valve 9,the fallback valve 29 is the normal closed (NC) type valve, when acurrent is applied by the controller 10, the fallback valve is opened,and in a state in which a current is not applied and shut off, thefallback valve is always maintained in closed state.

The present disclosure is configured such that, under a situation inwhich the electric booster 11 is in the backup mode, when all the firstcut valve 7 and the second cut valve 9, which are the normal open typevalves, are in opened state, a current is shut off and the fallbackvalve 29 is closed by the controller 10.

Due to the above, the second hydraulic pressure supply line 24 becomesin a state in which a flow passage thereof is blocked by the fallbackvalve 29, so that the wheel brakes 28 (calipers) of both the rear wheelsRL and RR become in a state in which the brake liquid pressure cannot besupplied thereto.

Since the second hydraulic pressure supply line 24 is blocked by thefallback valve 29 when the brake device enters the backup mode, eventhough the driver operates the brake pedal 2, the brake liquid pressure(hydraulic pressure of the master cylinder) caused by the pedaling forceis not transmitted to the rear wheel brakes 28 of both the rear wheelsRL and RR.

Eventually, in a state in which both the first cut valve 7 and thesecond cut valve 9 are opened after the brake device enters the backupmode, the brake liquid pressure caused by the pedaling force of thebrake pedal is transmitted to the piston in the cylinder of the caliperin the wheel brakes 28 of the front wheels FL and FR through the firstbackup line 6 and the first hydraulic pressure supply line 23 togenerate a braking force.

On the other hand, in the wheel brakes 28 of the rear wheels RL and RR,in a state in which the brake liquid pressure caused by the pedalingforce of the brake pedal is not transmitted to the piston in thecylinder of the caliper, control of forward and backward movements ofthe piston caused by an electronic parking brake (EPB) actuator can besmoothly performed.

Therefore, EPB cooperative control (dynamic parking brake control) canbe normally performed by the controller 10 to enhance a brakingdeceleration of the vehicle, an accurate braking control for the rearwheels is also possible by the dynamic parking braking using the normalEPB cooperative control, and by generating the required braking force onthe rear wheels by means of the dynamic parking braking, it is possibleto assist the braking deceleration of the vehicle.

In the normal mode, of course, since a current is applied to thefallback valve 29 so that the fallback valve is always maintained inopened state, when the driver operates the brake pedal 2, the brakeliquid pressure generated by the liquid pressure supply device 20 can benormally supplied to the wheel brakes 28 of both the rear wheels RL andRR through the second hydraulic pressure supply line 24, and normal rearwheel braking can be performed.

A method for controlling the brake device is described with reference toFIG. 4. When diagnosis for the brake device including the electricbooster 11 is made by the controller 10 and the brake pedal is operatedby the driver, the controller 10 receives a signal from the pedal sensor3 indicating that the brake pedal 2 is operated.

Then, when the brake pedal is operated (S11), if it is diagnosed that anabnormality or malfunction of the electric booster 11, an abnormality ormalfunction of the brake device occurs, the brake device enters thebackup mode (S12, S18).

The above described diagnosis process has been already performed in theknown brake device, and thus a detailed description thereof will beomitted.

When the brake device enters the backup mode, the controller 10 shutsoff the current of the fallback valve 29 to allow the fallback to becomein closed state (S19). Therefore, the wheel brakes 28 of both the rearwheels RL and RR become in a state in which the brake liquid pressure(hydraulic pressure of the master cylinder) caused by the pedaling forceof the brake pedal is not transmitted thereto through the hydrauliclines 8 and 24, but is shut off.

Further, then the brake device enters the backup mode, the EPBcooperative control for the dynamic parking braking to the rear wheelsRL and RR can be normally performed by the controller 10 (S21), and thusthe normal braking control generating the required braking force can beperformed for the rear wheels RL and RR.

Of course, since the brake liquid pressure caused by the pedaling forceof the brake pedal is transmitted to the wheel brake 28 on both thefront wheels FL and FR through the hydraulic lines 6 and 23, it is alsopossible to generate the required braking force for the front wheels.

Meanwhile, when it is determined in the step S12 that the brake deviceincluding the electric booster 11 is in a normal state, a state in whicha current is applied to the fallback valve 29, the first cut valve 7 andthe second cut valve 9 is maintained by the controller 10, and thus thefallback valve 29 which is the normal closed type valve is opened (S13),while the first cut valve 7 and the second cut valve 9, which are thenormal open type valves, are closed (S14).

Subsequently, the liquid pressure is generated by operation of theliquid pressure supply device 20 and is transmitted to the wheel brake28 of each of the front wheels FL and FR and the rear wheels RL and RR(S15, S16 and S17), and the braking in the normal mode is performed forthe front wheels and the rear wheels.

Conventionally, in a vehicle equipped with an integrated electricbooster which is an electronic system, when a system malfunction occurs,a driver could instantaneously feel braking inconvenience (stiffness ofthe brake pedal), causing a crash accident. In the brake deviceaccording to the present disclosure as described above, however, sincethe improved hydraulic circuit capable of shutting off the brake liquidpressure caused by the pedaling force of the brake pedal to the wheelbrakes of both the rear wheels is applied, the EPB cooperative controlfor the dynamic parking braking can be stably performed, and there is anadvantage in that a braking system becomes robust and field claim isprevented in advance.

As described above, according to the brake device and the method forcontrolling the same in accordance with the present disclosure, sincethe EPB cooperative control process such as the dynamic parking brakingcan be stably performed in a state in which the brake device enters thebackup mode of the integrated electric booster, it is possible to avoidcollision and accident occurrence due to insufficient brakingdeceleration of the vehicle in the backup mode, and to improve brakingperformance and running stability of the vehicle.

Further, according to the brake device and the method for controllingthe same according to the present disclosure, through a simpleimprovement such as adding the valve, which interrupts the circuit inthe backup mode, in the hydraulic circuit of the brake device using theintegrated electric booster (IEB), accordingly, the braking decelerationof the vehicle in the backup can be enhance and stability can besecured.

While the present disclosure has been described in detail with referenceto exemplary embodiments thereof, the scope of the present disclosure isnot limited to the above embodiments, and various modifications andimproved forms which is made by those skilled in the art using the basicconcept of the present disclosure as defined in the appended claims arealso included in the scope of the present disclosure.

What is claimed is:
 1. A brake device for a vehicle provided with anelectric booster and an electronic parking brake, comprising: a mastercylinder configured to receive pedaling force outputted from theelectric booster and generate brake liquid pressure; a liquid pressuresupply device configured to generate the brake liquid pressure accordingto a driver's pedal-operational value detected by a brake pedal sensorand supply the brake liquid pressure to a wheel brake of each wheel; ahydraulic pressure supply line connected from the liquid pressure supplydevice to the wheel brake of each wheel to enable the brake liquidpressure to be supplied from the liquid pressure supply device to thewheel brake; a backup line connected from the master cylinder to thehydraulic pressure supply line to enable the brake liquid pressure to besupplied from the master cylinder to the hydraulic pressure supply line;a cut valve disposed on the backup line and configured to selectivelyshut off the brake liquid pressure; and a fallback valve disposed on thehydraulic pressure supply line connected to the wheel brake of the wheelon which the electronic parking brake is installed, the fallback valvebeing configured to selectively shut off the brake liquid pressuresupplied to the wheel brake.
 2. The brake device of claim 1, wherein thewheel on which the electronic parking brake is installed is a rearwheel, and the fallback valve is disposed on the hydraulic pressuresupply line connected to supply the brake liquid pressure from theliquid pressure supply device to the wheel brake of the rear wheel. 3.The brake device of claim 1, wherein the fallback valve is a normalclosed type valve that is opened when a current is applied thereto andis closed when the current is shut off.
 4. The brake device of claim 1,wherein the fallback valve is installed at a downstream point of thehydraulic pressure supply line with respect to a point where the backupline is connected to the hydraulic pressure supply line.
 5. The brakedevice of claim 1, wherein the cut valve is a normal open type valvethat is closed when a current is applied thereto and is opened when thecurrent is shut off.
 6. The brake device of claim 1, further comprisinga controller configured to control the electronic parking brake and thefallback valve, wherein the controller diagnoses a state of the brakedevice including the electric booster and enters a backup mode in a casewhere the brake device is in a malfunction state when a driver operatesa brake pedal, and in the back mode, controls the fallback valve tobecome in a closed state and simultaneously performs dynamic parkingbrake control in which braking force for vehicle deceleration isgenerated by using the electronic parking brake.